ANATOMY AND PHYSIOLOGY:
Every cell in the human body needs energy in order to function. The body’s primary energy
source is glucose, a simple sugar resulting from the digestion of foods containing carbohydrates
(sugars and starches). Glucose from the digested food circulates in the blood as a ready energy
source for any cells that need it. Insulin is a hormone or chemical produced by cells in the
pancreas, an organ located behind the stomach. Insulin bonds to a receptor site on the outside of
cell and acts like a key to open a doorway into the cell through which glucose can enter. Some of
the glucose can be converted to concentrated energy sources like glycogen or fatty acids and
saved for later use. When there is not enough insulin produced or when the doorway no longer
recognizes the insulin key, glucose stays in the blood rather entering the cells.
Homeostasis depends on the precise regulation of the organ and organ systems of the body. The
nervous and endocrine system are two major systems responsible for that regulation. Together
they regulate and coordinate the activity of nearly all other body structures. When these system
fail to function properly, homeostasis is not maintained. Failure ofsome component of the
endocrine system to function can result in disease such as Diabetes Mellitus or Addison’s
The regulatory function of the nervous system and endocrine systems are similar in some
respects, but they differ in other important ways. The nervous system controls the activity of
tissues by sending action potentials along axons, which release chemical signals at their ends,
near the cell they control. The endocrine system releases chemical signals into the circulatory
sytem, whichh carries to all parts of the body. The cell that can detect those chemical signal
The nervous system usually acts quickly and has short term effects, whereas the endocrine
system usually response more slowly and has longer-lasting effects. In general, each nervous
stimulus controls a specific tissue or organ, whereas each endocrine stimulus controls several
tissues or organ.
• It regulates water balance by controlling the solute concentratiuon of the blood.
• It regulates uterine contractions during delivery of the newborn and stimulates milk
release from the breast in lactating females.
• It regulates the growth of many tissues, such as bone and muslces, and the rate of the
metabolism of many tissues, which helps maintain a normal body temperature and
normal mental function. Maturation of tissues, which result in the development of adult
features and adult behavior, are also influence by the endocrine system.
• It regulaytes sodium, potassium and calcium concentrations in the blood.
• It regulates the heart rate and blood pressure and helps prepare the body for physical
• It regulates blood glucoce levels and other nutrient levels in the blood
• It helps control the production and function of immune cells
•It controls the development and the function of the reproductive systems in males and
an elongated gland extending from the duodenum to the spleen; consist of a head, body,
and the tail. There is an exocrine portion, which secretes digestive enzymes that are
carried by the pancreatic duct to the duodenum, and pancreatic islet, which secrete insulin
The endocrine part of the pancreas consists of pancreatic islets (small islands; islet of
Langerhans) dispersed among the exocrine portion of the pancreas. The islets secrete two hormones –
insulin and glucagon—which function to help regulate blood nutrient levels, especially blood glucose.
Alpha cells of the pancreatic islets secrete glucagon.
Beta cells of the pancreatic islet secrete insulin.
It is very important to maintain blood glucose levels within a normal range of values. A
decline in the blood glucose levels within a normal range causes the nervous system to
malfunction because glucose is the nervous system’s main source of energy. When blood
glucose decreases, other tissues to provide an alternative energy source break fats and
proteins rapidly. As fats are broken down, the liver to acidic ketones, which are release
into the circulatory system, converts some of the fatty acids. When blood glucose level
are very low, the break down of fats can cause the release of enough fatty acid and
ketones to cause the pH of the fluids to decrease below normal, a condition called
acidosis. The amino acids of proteins are broken down and used to synthesize glucose by
If blood glucose levels are too high, the kidneys produce large volumes of urine
containing substantial amounts of glucose because of the rapid loss of water in the form
of urine, dehydration result
Insulin is released from the beta cells primarily response to the elevated blood glucose
levels and increased parasympathetic stimulation that is associated with digestion of a
meal. Increase blood levels of certain amino acids also stimulates insulin secretion.
Decreased result from decreasing blood glucose levels and from stimulation by the
sympathetic of the nervous system. Sympathetic stimulation of the pancreas occurs
during physical activity. Decreased insulin levels allow blood glucose to be conserved to
provide the brain with adequate glucose and to allow other tissues to metabolize fatty
acids and glycogen stored in the cell.
The major target tissues for insulin are the liver, adipose tissue, muscles, and the area of
the hypothalamus that controls appetite, called satiety center (fulfillment of hunger).
Insulin binds to membrane-bound receptor and, either directly or indirectly, increases the
rate of glucose and amino acid uptake in these tissues. Glucose is converted to glycogen
or fat, and the amino acids used to synthesize protein.
Glucagon is released from the alpha cell when blood glucose level is low. Glucagon binds
to membrane-bound receptors primarily in the liver and caused the conversion of
glycogen storage in the liver to glucose. The glucose is then released into the blood to
increase blood glucose level. After a meal, when blood glucose levels are elevated a
glucagon secretion is reduced.
Insulin and glucagon function together to regulate blood glucose levels. When blood
glucose increase, insulin secretion increases, and glucagon secretion decreases. When
blood glucose levels decrease, the rate of insulin secretion declines and the rate of
glucagon secretion increase. Other hormones, such as epinephrine, cortisol, and growth
hormones, also function to maintain blood levels of nutrients. When blood glucose level
decrease, these hormones are secreted at a greater rate. Epinephrine and cortisol caused
the breakdown of protein and fat and the synthesis of glucose to help increase blood
levels of nutrients. Growth hormone slows protein breakdown and favors fat breakdown